Electric power restructuring began in the United States in 1978 with enactment of the Public Utility Regulatory Policy Act (PURPA). PURPA established competition in power generation, forcing utilities to purchase power from independent generators at prices equal to their "avoided costs." Independent power producers flourished and by 1993 more than 50% of all new generation plants were by independents, dispelling the notion that economies of scale necessitated a natural monopoly on electricity generation by utilities. Restructuring continued in the United States with enactment of the Energy Policy Act of 1992, which permits wholesale customers a choice of suppliers and requires utilities to transport power across their grids to accomplish this ("wheeling"). Although the 1992 Act prohibits federal mandating of retail wheeling, it allows states to permit this, and many states are considering doing so. Sally Hunt and Graham Shuttleworth, Unlocking the Grid, IEEE Spectrum 33:7, July 1996, p. 20.
It is envisioned then, that deregulation will likely enable utilities and power brokers to buy and sell electricity at real-time rates determined by supply and demand, much like other commodities. In order for this to occur, however, technology must be able to measure and communicate energy usage on a real-time basis
Historically, utility companies have used meter reading personnel to literally read and record the consumed commodity information provided by utility meters (i.e., gas, water, electricity and the like). However, in recent years significant strides have been made in the deployment of fully Automatic Meter Reading (AMR) systems.
Most remote meter reading systems have similarities in their designs. Generally, they comprise three major subsystems: (1) some type of encoder device physically attached to a meter and electronically connected to an end device (AMR) to give an indication of the meter reading, (2) means for storing the meter reading indicated, usually a dedicated microcontroller, and (3) means for transmitting meter data over a communication link to a central station. Various types of communication links have been used to transfer the meter data from the individual end devices to the central station:
Wireless
One wireless system utilized a mobile van carrying a radio transmitter for interrogating meter-reading end devices which include transponders. The interrogated radio transponders would then return messages to the van, which messages include meter identification and readings. Another system is based upon technology similar to that of cellular phones; radio transponders are installed throughout the metropolitan area in order to relay such messages to and from the end devices.
Because of the need for large investments in infrastructure, these wireless systems are not feasible for servicing customers who are widely separated; examples are members of multiple competing "power pools" formed by emerging enterprises called "aggregators" to achieve economies of scale in their purchase of utility commodities.
Wired via Power Line Carrier
There exist arrangements in which the power lines of the subscriber and the electric utility company are used as the link between the customer's meter and the central station. One such arrangement is described in U.S. Pat. No. 4,135,181, comprising a central station which includes a computer with input-output equipment for the multiplex generation of commands and the multiplex receipt of data over a plurality of communication lines. The system also includes an end device located at each customer residence. Each end device is connected to the power line, and receives commands from and transmits messages to the control unit over the connecting power line. Each end device is capable of selectively communicating with a plurality of utility meter encoders for reading a plurality of meters and for selectively driving a plurality of loads at a customer residence.
Although power line carrier networks are useful for reaching customers within a geographically constrained area (e.g., metropolitan), they are not feasible for reaching customers arbitrarily located across a continent, or around the world.
Wired via Telephone
Using telephone lines for automatic reporting of meter and status data is well known. In some of these systems, an interrogation signal is sent from a central receiving station to an end device (reporting station) in order to initiate the transmission of a report, the end device being either located at a telephone exchange or being connected through a telephone line thereto. Such systems may involve ringing of the customer's telephone or the installation of special ring-suppression equipment at the customer's facility or, alternatively, special equipment at the telephone exchange.
In another type of system, an end device initiates the transmission of a report. For example, U.S. Pat. No. 3,098,13 (Stonor) discloses a system in which a pulse-dialing operation is automatically performed, followed by the transmission of a message to report the condition at the end device. U.S. Pat. No. 3,357,011 (Diaz) discloses a system in which the call-in time is controlled by a clock at the end device, the clock also being used to periodically trigger transfers of data to a local memory for later transmission to the central station upon command.
Other systems in which calls are made periodically or at preset times are disclosed in U.S. Pat. Nos. 3,046,339 (Breen); U.S. Pat. No. 3,294,910 (Jackson); U.S. Pat. No. 3,510,591 (Klein); U.S. Pat. No. 4,056,684 (Lindstrom); U.S. Pat. No. 4,086,434 (Bocchi); and U.S. Pat. No. 4,104,486 (Martin et al.). In the Klein system, a schedule of times to call in is sent to an end device to be stored in memory and to be compared with clock signals to make a call-back at a desired time. U.S. Pat. No. 4,020,628 (Vittoz) and U.S. Pat. No. 4,125,993 (Emile, Jr.) illustrate systems in which signals may be transmitted through a telephone line to regulate the frequency or set the time at a remote clock.
Much of the effort thus far has been directed at the residential AMR market, which is far larger than the industrial/commercial users targeted by aggregators, but of little interest to them. Consequently, the sharing of a telephone line is not an issue; most large users have in-house PBX systems and local area networks, offering very low incremental cost for a connection. Similarly, aggregators have little interest in the small initial savings per end device that many of these specialized circuits yield. They can well afford to invest in the next higher level of integration, the computer-on-a-board, because the increase in functions (via software) yields substantial reductions in operating costs. Conventional AMRs were designed specifically to perform a chore that the utility companies were required to do.
Computer and microprocessor technology has developed very rapidly. Since the mid 1970's, microprocessors have been commercially available at relatively low cost to perform many complex functions. In addition, restrictions on the connection of equipment to telephone lines were removed during the period 1970-1975. Currently (the mid 1990's), similar deregulation is occurring in the telephone and the electric power industries, while commercial restrictions on the use of the global computer information network have been abandoned.
What is needed to enable real-time continuous trading of utility commodities is an AMR system that sends hourly (or more often) readings from geographically dispersed end devices at a very low cost per reading. Ideally, costs should be minimized by connecting each end device to the most economical network available at a customer's facility: local telephone calls to an e-mail network, in-house network messages leading to e-mail via the global computer information network, or long distance calls of very short duration to the central station.